The present disclosure relates to imaging devices, and particularly to imaging device and imaging method to control driving of a lens and a program for causing a computer to carry out the method.
Imaging devices, such as digital still cameras, that perform imaging of a subject such as a person by using an imaging element to generate a taken image and record this generated taken image are prevalent. Furthermore, imaging devices having an autofocus function are widely prevalent. In addition, along with size reduction of the imaging element, optical system components, and so forth, portable information terminals equipped with these imaging devices (camera modules) are prevalent.
These portable information terminals are equipped with an actuator for moving the focus lens in the optical axis direction in order to realize the autofocus function. It is preferable that the amount of movement by this actuator linearly changes with respect to the applied voltage. However, it is becoming practical to use an element having the characteristic of hysteresis between the supplied voltage and the amount of movement of the focus lens (e.g. piezoelectric element) as the actuator for the purpose of reduction in the power consumption, size, and so forth of the actuator.
If an element having this hysteresis characteristic is used as the actuator, the accurate amount of movement is not obtained because an error occurs in the amount of movement. For this case, a focus control technique in which a position sensor of the focus lens is provided to thereby carry out feedback control to compensate the error and enhance the positioning accuracy is prevalent. However, providing the position sensor precludes size reduction of the imaging device and increases the cost. Thus, a device that uses the actuator having the hysteresis characteristic without a position sensor is being studied.
For example, as the imaging device including such an actuator, there has been proposed an imaging device that counts position information of the focus lens by using a counter counted depending on the supply time of a voltage supplied to a piezoelectric element and carries out positioning control of the focus lens (refer to e.g. Japanese Patent Laid-Open No. 2009-169013).